1. Field of the Invention
The invention relates to a method and an apparatus for producing bag packages.
2. Prior Art
Bag packages, in which foods such as powdered milk or flower, for instance, can be stored, are typically made from a sealable material, and have a base, in particular a block-type base suitable as a surface to stand on, and an angular, preferably rectangular cross section. To improve the stability of these bag packages, it is usual for the longest edges to be reinforced.
These edge reinforcements prevent deformation of the side walls and thus assure high dimensional stability of the bag package. The reinforcements for instance comprise sealing seams, which are produced by heat sealing in such a way that they need not perform any leakproofing function whatever. There are two common forms of bag; in one, the longitudinal seam is located centrally, and in the other it is located in the region of one edge. The longitudinal seam serves the purpose of stability and impermeability.
Apparatuses for producing these bag packages, known as tubular bag-making machines, form the bag packages with a rectangular cross section from packaging material sheeting. In one method step, the packaging material sheeting is folded over by a forming shoulder in such a way that a tube is produced. Next, in known methods, the edges are formed and sealed, so that the desired rectangular cross section is created and the bag package has the desired stability. Finally, the abutting edges are welded together, creating the longitudinal seam or longitudinal sealing seam.
German Patent 1 113 174 disclosure an apparatus for producing bag packages from one or more heat-sealable lengths of film in which feed devices are provided which comprise tongs or pairs of clamping jaws that can be raised and lowered. These elements are disposed such that the inside cross section of the forming mandrel is not altered by either the three-dimensional shape and disposition of the tongs nor their motion.
German Utility Model DE-GM 18 07 453 describes an apparatus for producing bag packages. In it, inside an optionally spreadable box form adapted to the initial bag cross section, edge strips adapted to the reduced bag cross section and extending preferably on both sides of the longitudinal edge of the bag are longitudinally displaceable and inserted with cushioning at the top. A pressure plate with heating plates pivotably connected to it that can be swivelled inward toward the bag walls can be pressed against the plate below the bag base. The lateral heating plates are pivotably connected and shaped in such a way that in cooperation with the edge strips located in the interior of the bag, the desired edge welding results at the base and at the side edges.
A disadvantageous aspect of known methods and apparatuses is that in the region downstream of the forming pipe, in which the edges are shaped and sealed, machine height is necessary.